Remote monitoring of heart action, or the action of other living organs has been heretofore performed by the use of implanted radio transmitters, usually energized by mercury cells or other chemical battery supply means. The operating life of such an implanted transmitter is limited by the relatively short operational life of the associated battery, as in the case of currently employed heart pacemaker apparatus.
Known radio telemetry systems of the self-powered type, such as that disclosed, for example, in U.S. Pat. No. 4,001,798 to Roland L. Robinson, are intended to provide continuous radio transmission energized by a transducer, the transducer serving both as a power generating means to drive the associated radio transmitter and as a means to modulate the transmitter, whereby to transmit the transduced signal. Since a considerable amount of power output is required from the transducer, for example, a piezoelectric crystal slab, said transducer must be relatively large and bulky. Although this presents no serious problems for industrial applications wherein there is usually ample space for the transducer and associated radio transmitting apparatus, it is not practical for biotelemetry systems where the apparatus is required to be implanted in a living body.
Previously used implantable biotelemetry transmitters (employing batteries, or the like, as power sources) are either continuously energized or turned on and off with a magnetic reed switch which can be activated from outside the body. All of the previously used approaches dictate short power supply life. There is a need for the usage in these systems of a biological energy converter wherein there is no depletion of a discrete quantity of power as occurs with a mercury cell or a nuclear reactor type of power supply.